HTC has upgraded its flagship smartphone, the One X, with a faster quad-core processor, twice the integrated storage capacity, a bigger battery and LTE in the U.S.

The HTC One X+ smartphone.

The new model is called the HTC One X+, and the company will be hoping that it can compete more successfully than its predecessor with Samsung's Galaxy S III and Apple's iPhone. Just like other vendors HTC has had a hard time keeping up with the smartphone market's two dominating forces.

The One X+ is powered by a 1.7GHz quad-core Nvidia Tegra 3 AP37 processor and has 64GB of integrated storage.

The processor upgrade will improve the overall performance of the phone, including smoother gaming and faster downloads, according to HTC. The original 3G model had a 1.5GHz quad-core processor.

HTC has also increased the size of the battery from 1,800mAh to 2,100mAh.

The screen still measures 4.7 inches and has the same 1280-by-720-pixel resolution, but it is now protected by Gorilla Glass 2. The phone's size is also the same, but it is 5 grams heavier.

In Europe, the smartphone will be 3G only, according to HTC's spec sheet. In the U.S., AT&T will have exclusive access to an LTE version that will still have the quad-core processor, the operator said on Tuesday.

But LTE has also started to take off in Europe. The Samsung Galaxy S III and the iPhone 5 both support LTE spectrum bands used in countries such as the U.K. and Germany.

HTC didn't immediately reply to questions about a One X+ with LTE for Europe. Details about the U.S. launch will be announced shortly, according to HTC.

On the software side, the One X+ will use Android 4.1 (also known as Jelly Bean), which will also be available for the One X and the One S from October.

The phone will start shipping in October in Europe and Asia. The U.S version will start shipping in the coming months, according to AT&T. Pricing was not announced.